Detailed studies of tumor-host immune interactions in animals and humans with sarcomas are being performed in an attempt to develop new immunodiagnostic and immunotherapeutic techniques for diagnosis and treatment of these tumors. Immune response to murine sarcomas has been extensively evaluated and both tumor-specific and fetal antigens have been identified. Fetal antigens have been identified on human osteogenic sarcomas and monoclonal antibodies are being developed using hybridoma techniques. Attempts are being made to develop adoptive immunotherapeutic techniques utilizing transfer of cells grown in long term culture in T cell growth factor. Techniques for the prolonged growth of cytotoxic T cells have been developed. These cells have been shown to mediate immunologic rejection of allografts and syngeneic tumors and attempts to use these cells for the adoptive immunotherapy of mouse and human tumors are in progress.